Gypsum panels, methods, and systems

ABSTRACT

Gypsum panels and methods of making gypsum panels are provided. A method of making a gypsum panel includes combining gypsum stucco and a halide salt sequestration agent with water to form a gypsum slurry and setting the gypsum slurry to form at least a portion of a gypsum core, wherein the halide salt sequestration agent is present in an amount effective to sequester at least a portion of halide salt present in the gypsum stucco. A gypsum panel includes a gypsum core that comprises set gypsum and a halide salt sequestration agent, wherein the halide sequestration agent sequesters at least a portion of halide salt present in the gypsum core.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit of U.S. Provisional PatentApplication No. 62/638,550, filed Mar. 5, 2018, the disclosure of whichis incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure generally relates to gypsum panels and methods ofmanufacturing gypsum panels, and particularly relates to gypsum panelsin which the impact of salt within the gypsum material has beenmitigated.

Panels having a core of set gypsum have long been used as structuralelements in the fabrication of buildings. Such panels, also commonlyknown as “wallboard,” “drywall,” or “plasterboard,” are typically usedto form the partitions or walls of rooms, elevator shafts, stairwells,ceilings and the like and represent a less costly and more expeditiousalternative to conventional plaster walls.

In its most common form, gypsum wallboard is produced by sandwiching asolid gypsum core made from an aqueous slurry of calcined gypsum,usually a slurry of calcium sulfate hemihydrate, between two sheets of afacing material, typically heavy papers or fibrous mats, such asfiberglass. Gypsum wallboard is manufactured continuously at a highspeed by continuously depositing the aqueous slurry of calcined gypsumand other ingredients onto one of the two facing sheets and thenbringing the second facing sheet into contact with the free surface ofthe gypsum slurry to form a sandwich-like structure.

The calcined gypsum slurry deposited between the two facing sheets sets(i.e., the calcined gypsum reacts with water from the aqueous slurry) toform a rigid board-like structure. The so-formed board then is cut intopanels of a desired length (for example, eight to sixteen feet). If theso-formed board contains excess water (water is necessary not only forhydrating the calcined gypsum but also to ensure sufficient fluidity ofthe gypsum slurry during preparation of the board), the board may thenpass through a drying kiln in which excess water is removed and thegypsum wallboard is brought to a final hydrated, but dry state. Afterthe core has been set and is fully dried, the sandwich becomes a rigid,fire-resistant building material.

However, it would be desirable to produce gypsum panels having improvedstrength and/or an improved bond between the gypsum core and the panelfacer material.

SUMMARY

In one aspect, a method of making a gypsum panel is provided, includingcombining gypsum stucco and a halide salt sequestration agent with waterto form a gypsum slurry, and setting the gypsum slurry to form at leasta portion of a gypsum core, wherein the halide salt sequestration agentis present in an amount effective to sequester at least a portion ofhalide salt present in the gypsum stucco.

In another aspect, a gypsum panel is provided, including a gypsum corethat contains set gypsum and a halide salt sequestration agent, whereinthe halide sequestration agent sequesters at least a portion of halidesalt present in the gypsum core.

In yet another aspect, sheathing systems are provided, including atleast two of the gypsum panels described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, which are meant to be exemplary and notlimiting, and wherein like elements are numbered alike. The detaileddescription is set forth with reference to the accompanying drawingsillustrating examples of the disclosure, in which use of the samereference numerals indicates similar or identical items. Certainembodiments of the present disclosure may include elements, components,and/or configurations other than those illustrated in the drawings, andsome of the elements, components, and/or configurations illustrated inthe drawings may not be present in certain embodiments.

FIG. 1 is a cross-sectional view of a gypsum panel having a papermaterial facer

FIG. 2 is a cross-sectional view of a gypsum panel having two papermaterial facers.

FIG. 3 is a schematic depiction of a process of producing a gypsumwallboard.

FIG. 4 is a perspective view of a building sheathing system.

FIG. 5 is a graph showing the results of the humid bond test of Example1.

FIG. 6 is a graph showing the results of the humid bond test of Example2.

FIG. 7 is a graph showing the results of the nail pull test of Example2.

FIG. 8 is a graph showing the results of the ion chromatography tests ofExample 3.

FIG. 9 is a graph showing the results of the ion chromatography tests ofExample 3.

FIG. 10 is a graph showing the results of the ion chromatography testsof Example 4.

FIG. 11 is a graph showing the results of the ion chromatography testsof Example 5.

FIG. 12 is a graph showing the results of the humid bond test of Example6.

FIG. 13 is a graph showing the results of the humid bond test of Example6.

DETAILED DESCRIPTION

Gypsum panels and systems of panels, and methods for their manufacture,are provided herein. The panels display improved strength and/or animproved bond between the gypsum core and the panel facer material. Inparticular, the panels may display a relatively high bond strengthbetween the gypsum core and a paper facer material.

The raw gypsum used to create gypsum panels is obtained from variousnatural sources as well as from flue gas desulfurization (FGD) (alsoknown as byproduct or synthetic gypsum), which is obtained from electricutilities. As such, the chemical composition of the gypsum may varysignificantly between sources. These differences in the chemicalcomposition have been discovered to result in differences in resultingpanel performance, including strength and bond between the core and thefacer material. In particular, it has been discovered that the presenceof salt in the gypsum may negatively affect panel performance in theseareas. The present disclosure is directed at methods for mitigating theimpact of salt on these performance characteristics. In particular, thisdisclosure is directed to methods for making gypsum panels by combininga halide salt sequestration agent with the gypsum stucco, in an amounteffective to sequester at least a portion of any salt present in thegypsum stucco, as well as panels and systems of panels produced by thesemethods.

Methods of making gypsum panels, and the resulting panels, will bedescribed in detail. It should be understood that although features ofthe disclosure may be described with reference to particularembodiments, the disclosure is meant to encompass any number ofvariations, alterations, substitutions, or equivalent arrangements notexplicitly described herein, and should not be limited to suchexplicitly disclosed embodiments.

Methods of Making Gypsum Panels

In one aspect, methods of making gypsum panels to mitigate the impact ofsalt present in the gypsum stucco are provided. In certain embodiments,these methods include combining gypsum stucco and a halide saltsequestration agent with water to form a gypsum slurry, and setting thegypsum slurry to form at least a portion of a gypsum core, wherein thehalide salt sequestration agent is present in an amount effective tosequester at least a portion of halide salt present in the gypsumstucco. These methods may be used to produce gypsum panels having any ofthe features, or combinations of features, described herein.

As used herein the phrase “halide salt sequestration agent” refers to amaterial that is effective to capture or bind to a halide ion (e.g.,chloride, fluoride, bromide) of a halide salt, to render it inactive.For example, halide salts may include sodium chloride (NaCl), calciumchloride (CaCl₂)), potassium chloride (KCl), potassium iodide (KI),lithium chloride (LiCl), copper(II) chloride (CuCl₂), silver chloride(AgCl). For example, the halide salt sequestration agent may act tosequester the halide ion through any suitable mechanism. In certainembodiments, the halide salt sequestration agent has a porous surfacethat provides increased surface area to capture the halide salt.

As used herein, the phrase “in an amount effective to sequester at leasta portion of halide salt present in the gypsum stucco” refers to theagent rendering inactive at least some portion of the halide ionspresent in the gypsum stucco, if any are present. For example, thehalide salt sequestration agent may be provided in an amount effectiveto sequester at least 25 percent, by weight, of the halide salts presentin the gypsum stucco. For example, the halide salt sequestration agentmay be provided in an amount effective to sequester at least 50 percent,by weight, at least 75 percent, by weight, at least 90 percent, byweight, or at least 95 percent, by weight, of the halide salts presentin the gypsum stucco.

In certain embodiments, the halide sequestration agent is alumina (i.e.,aluminum oxide), perlite (amorphous volcanic glass containing siliconoxide and/or aluminum oxide, among other compounds), or a combinationthereof. Other suitable materials that are effective at sequesteringhalide ions may also be used. For example, the alumina may be activatedalumina, which is manufactured from aluminum hydroxide bydehydroxylating it in a way that produces a highly porous material witha relatively high surface area to weight ratio. For example, the aluminamay have a surface area of about 200 m²/g or greater, such as of about300 m²/g or greater.

In certain embodiments, the halide salt sequestration agent includesactivated alumina present in an amount of from about 0.01 to about 10weight percent, by weight of the gypsum stucco. In some embodiments, theactivated alumina is present in an amount of from about 0.01 to about 3weight percent, by weight of the gypsum stucco. The alumina may have arelatively small particle size, so as to increase the available surfacearea of the agent for a given mass of material. For example, the aluminamay have an average particle size of less than about 5 mm, such as lessthan about 4 mm, less than about 2 mm, or less than about 1 mm.

In certain embodiments, the halide sequestration agent includes perlitepresent in an amount in an amount of from about 0.01 to about 10 weightpercent, by weight of the gypsum stucco. In some embodiments, theperlite is perlite ore. In other embodiments, the perlite is expandedperlite. For example, the perlite ore may have an average particle sizeof less than (i.e., a smaller particle than) 30 mesh. For example, theperlite ore may have a particle size range displaying the followingscreen analysis (screen size; maximum range and minimum range cumulativetotal percent by weight retained): (16 mesh; --/3; --/0); (20 mesh;7/15; 0/5); (30 mesh; 35/42; 12/25); (50 mesh; 95/98; 75/80); (100 mesh;100/100; 95/95). For example, the expanded perlite may have an averageparticle size of less than (i.e., a smaller particle than) about 16mesh. For example, the expanded perlite may have a particle size rangedisplaying the following screen analysis (screen size; cumulative totalpercent by weight retained): (8 mesh; 0); (16 mesh; 1-11); (20 mesh;41-69); (30 mesh; 68-88); (50 mesh; 93-96); (100 mesh; 96-100).

In certain embodiments, methods of manufacturing these gypsum panelsfurther include heating the halide sequestration agent (e.g., perlite,alumina, unexpanded aluminum oxide) prior to combining the halidesequestration agent with the gypsum stucco. For example, the heating iseffective to expand or activate at least a portion of the halidesequestration agent. That is, the methods may include a step of formingthe expanded perlite or activated alumina. Such heating may be done onor off-line with the gypsum panel formation, such as in a kiln, kettle,oven, or other suitable heating apparatus.

As in any gypsum wallboard, the largest single ingredient, other thanpossibly water, in the gypsum slurry is a source of calcined gypsum,usually calcium sulfate hemihydrate, commonly referred to as “stucco” or“Plaster of Paris.” Generally, a wide amount of calcined gypsum can beused in preparing the gypsum slurry. The calcined gypsum typicallycomprises about 30 weight percent to about 60 weight percent of thegypsum slurry, such as from about 40 to 50 weight percent of the gypsumslurry. However, this disclosure is not limited to any particular sourceof the calcined gypsum and can use calcined gypsum made from bothnatural minerals extracted from quarries, and from synthetic gypsums,known as desulfogypsum, produced from the desulfurization of electricalpower plant flue gas effluents (i.e., FGD gypsum). Calcined gypsum madefrom a combination of natural and synthetic gypsum also can be employed.Following hydration and drying, the set gypsum typically constitutesmore than 85 percent, by weight, of the set gypsum core.

Whether natural rock or synthetic, the gypsum may be dried, ground,calcined, and stored as stucco, which is calcium sulfate hemihydrate.The drying step of stucco manufacture typically includes passing crudegypsum rock through a rotary kiln to remove free moisture, and thengrinding the rock to a desired fineness, using for example a rollermill. The dried, ground gypsum, often referred to as “land plaster,”then is typically heated in a “calciner” to remove water of hydrationand yield the calcined gypsum that exhibits the valuable property ofbeing chemically reactive with water, and setting to form a rigidstructure. There are two forms of stucco, alpha (α) calcium sulfatehemihydrate and beta (β) calcium sulfate hemihydrate. As will beappreciated by those skilled in the art, these two types of stucco areproduced by different calcination procedures. The present disclosure cangenerally use either the beta or the alpha form of stucco; though, as isthe case in conventional gypsum wallboard production, the less costlybeta form is usually used.

In certain embodiments, the calcined gypsum is mixed, typically in a“pin” mixer, with the halide salt sequestration agent and any otheradditives, in the presence of water, to form a gypsum slurry. In someembodiments, the halide salt sequestration agent is dry mixed with thegypsum stucco; however, other processes may also be used. Thus, theaqueous gypsum slurry contains at least gypsum, water, and the halidesalt sequestration agent; however, other additives will commonly beused. For example, any suitable additives known in the industry may beused. For example, suitable additives may include starches (such asregular and pregelatinized starch), agents to reduce the density of thegypsum core (such as foaming agents, surfactants, microspheres),dispersants, set retarders, set accelerators, biocides (mold and mildewcontrol agents), fillers, water resistance additives (such as a wax or awax emulsion or siloxanes), fire retardants, reinforcing fibers (such aschopped glass fibers or other inorganic fibers), strength-enhancingagents (such as sodium trimetaphosphate or polymeric binders) andcombinations thereof.

An amount of water also is included in the gypsum slurry to ensureproper flowability of the slurry. Water is added to the process tohydrate the calcined gypsum, to provide needed fluidity. As is the casein conventional wallboard production, most of this water must eventuallybe driven off by heating the set gypsum wallboard. Thus, the lower theamount of water used, the lower the drying costs. In certainembodiments, the weight ratio of water to calcined gypsum can range overa wide range of weight ratios (i.e., weight of water divided by weightof calcined gypsum). In some embodiments, the water-to-calcined gypsumweight ratio (water:calcined gypsum) is established in the range ofabout 0.5:1, to about 1.5:1, such as from about 0.7:1 to about 1.3:1.

The gypsum slurry may be formed into a long, continuous sheet betweentwo layers of facing material. In an alternative embodiment, the gypsumslurry may be placed in a mold.

One method for preparing a wallboard in accordance with the presentdisclosure is illustrated schematically in FIG. 3. In this embodiment,the calcined gypsum is fed into the top of a mixer of the type commonlyreferred to as a pin mixer (not shown) along with other dry components.In particular, the halide salt sequestration agent and any otheroptionally included dry additive components from which the gypsum slurryis formed can be pre-mixed and then fed as a dry mixture to the pinmixer. Water and other liquid constituents (e.g., soap or foam, preparedseparately using high shear mixing and used to control the slurrydensity), used in forming the gypsum slurry, are also metered into thepin mixer through other ports where they are combined with the drycomponents to form an aqueous gypsum slurry 41, which emerges from adischarge conduit 40 of the pin mixer. The residence time in the pinmixer usually is very short.

The slurry is deposited through one or more outlets of the dischargeconduit 40 onto a continuous, horizontally moving lower facing sheet 24comprising a facing material (e.g., paper, a fibrous web) which may beslightly wider than the desired width of the wallboard. The lower facingsheet 24 and the deposited gypsum slurry 41 move in the direction ofarrow B. An upper facing sheet 22, also including a material such aspaper, is fed in the direction of arrow C from a roll (not shown) andapplied to the upper surface of the gypsum slurry 41. The “sandwich” ofslurry and adjacent facing sheets is then passed through a mold or otherforming device (rollers, guides, or plates (50 and 52)) for establishingthe desired width and thickness of the gypsum board. The amount ofslurry deposited can be controlled in a manner known in the art suchthat it, in cooperation with plates 50 and 52 and the facing sheets 22and 24, form a board of the desired width and thickness. Facing sheets22 and 24 are usually of a type of paper, such as multi-ply paper,commonly used for the face sheet of wallboard products, or a fibrousweb, such as fiberglass, although other facing materials may be used.

The lower facing sheet 24 is fed from a roll (not shown). In someembodiments, prior to receiving the gypsum slurry 41, the lower facingsheet 24 may be scored by one or more scoring devices, allowing theedges of lower facing sheet 24 to be folded upward and around thedeposited gypsum slurry. These edges may then be glued or adhered with agypsum slurry to overlapping portions of an upper facing sheet 22according to methods known in the art. Prior to applying the (upper)facing sheet 22 to the upper surface of the gypsum slurry, glue may beapplied to the facing sheet along portions of the sheet that willoverlap and be in contact with the folded-over mat edges (glueapplication is not shown).

In certain embodiments, the gypsum core includes multiple layers thatare sequentially applied to the fiberglass mat, and allowed to seteither sequentially or simultaneously. In other embodiments, the gypsumcore includes a single layer. Though not shown, the present disclosurealso contemplates that, in certain embodiments, a minor portion of thegypsum slurry may be discharged through an appropriate outlet to providea relatively thin layer of gypsum slurry on the inner surface of facingsheets 22 and 24. The thin layer of gypsum slurry is somewhat denserthan the aqueous slurry of gypsum used to form the main portion of theset gypsum core (main core slurry discharged through outlet 40 to formgypsum slurry layer). This higher density region of the core (also knownas the “slate coat”) is intended to assist in the formation of a strongbond between the lower density portion of the core and the facingsheets, such as by penetrating into the interstices of a fibrous facingmaterial.

In some embodiments, the slurry used to form the slate coat layer isabout 18 to 20 percent denser than the density of the slurry used toform the main portion of the set gypsum core. In certain embodiments,depositing the gypsum slurry includes depositing a first gypsum slurryhaving a wet density of from about 88 pcf to about 98 pcf onto thesurface of a fiberglass mat, the first gypsum slurry. In certainembodiments, the first gypsum slurry has a wet density of from about 93pcf to about 96 pcf. In some embodiments, the gypsum core includes atleast three gypsum layers, with the outermost gypsum layers of thegypsum core (i.e., the layers that form an interface with the facermats) being slate coat layers. In certain embodiments, both outermostlayers have a relatively high density or are otherwise chemicallyaltered for enhanced penetration. Thus, a third gypsum slurry may have awet density of from about 88 pcf to about 98 pcf, or from about 93 pcfto about 96 pcf. In certain embodiments, the first gypsum slurry (oreach of the outermost gypsum slurry layers) is deposited in an amount offrom about 5 percent to about 20 percent, by weight, of the gypsum core.In addition, it also is contemplated that, in some embodiments, some ofthis higher density gypsum slurry also can be used to form streams ofgypsum slurry at each of the edges of the facing sheets to form hardedges of the wallboard.

In the illustrated embodiment, the nascent board 16 then travels onrollers or on a conveyor 54 in the direction of arrow D for severalminutes. During this time, the slurry is allowed to set and form thehardened gypsum core by hydration of the stucco. During this settingprocess, the core hardens as the gypsum mineral (calcium sulfatedihydrate) is formed.

Wallboard panels are then cut to length, flipped, and dried, such as ina continuous oven or by allowing the material(s) to set at roomtemperature (i.e., to self-harden). The individual boards may then betaped face-to-face in pairs and stacked for shipment. For moldedarticles, the gypsum slurry is alternatively introduced directly into amold and the slurry sets to form the article.

As noted above, in certain embodiments, the slurry contains more waterthan necessary solely to reconstitute the gypsum from stucco. This extrawater is used in the board forming stage to reduce the stucco slurryviscosity sufficiently to allow for its even distribution (e.g., byusing a forming roll) across and between the facing sheets at a desiredthickness. Because of the use of excess water, the gypsum board remainswet after hydration (although it is possible at this point the board canbe cut to desired dimensions). Therefore, the formed board ultimatelymay be dried.

In certain embodiments, the drying operation involves applying heat bycirculating hot air (e.g., in a drying oven) around the wet gypsum boardto evaporate the excess water. It may be necessary, therefore, that thefacing sheets be sufficiently porous to allow this excess water toreadily evaporate without adverse effects such as delamination, tearing,bursting, etc. of the facing sheets. The ability of the facing sheets toallow the escape of water vapor may also promote a uniform degree ofdryness. This may improve overall board quality, since insufficientlydried gypsum board presents storage problems, while over-drying leads tocalcination and causes a loss of mechanical strength. Typical dryingconditions may involve maintaining an ambient or surrounding hot airtemperature from 200° F. to 600° F. (about 95° C. to 315° C.) for adrying time from 10 minutes to 2 hours. For example, at line speeds ofabout 70 to about 600 linear feet per minute, drying times of about 30to about 60 minutes may be used. However, these parameters are exemplaryand are influenced by the particular configuration of the boardmanufacturing line.

Conventional gypsum wallboard, at a nominal thickness of ½ inch or ⅝inch, typically is prepared at a weight between about 1200 to 2000pounds per 1,000 square feet (MSF) of board (about 5,900 kg to about9,800 kg per thousand square meters). This corresponds to a boarddensity of about 38 to about 43 lb/ft′ (about 0.61 to 0.69 g/cc). Thegypsum wallboards prepared in accordance with this disclosure may havesuch relatively high weight and densities, or may have a reduced densityrelative to a standard wallboard. For example, reducing the weight ofeach gypsum wallboard panel by as little as 30 pounds/MSF can result insignificant savings. For example, by adjusting the proportion of foam inthe gypsum slurry, the set gypsum core of the present disclosure mayhave a much lower density than commercially available gypsum products.In certain embodiments, a gypsum wallboard of the present disclosure ata nominal thickness of ½ inch has a weight between about 1000 to 1300pounds per MSF of board. This corresponds to a density of about 24 toabout 31 lb/ft′ (about 0.38 to 0.50 g/cc).

In certain embodiments, the gypsum core includes about 80 weight percentor above of set gypsum (i.e., fully hydrated calcium sulfate). Forexample, the gypsum core may include about 85 weight percent set gypsum.In some embodiments, the gypsum core includes about 95 weight percentset gypsum.

The facing sheets, also referred to interchangeably herein as “facermaterials” or “facer mats”, may comprise any fibrous material known tobe suitable for facing gypsum board. Specific materials include paper,such as heavy, single, or multi-ply paper (e.g., medium or heavy Kraftpaper, manila paper, etc.) and cardboard. For example, multi-ply paperused for the facing sheet of gypsum board products may have a basisweight from 40 to 65 pounds per MSF, an overall caliper of 250 to 350microns, and a Gurley porosity from 15 seconds to 145 seconds. In someembodiments, different types of paper are used for each gypsum boardsurface. For example, manila paper may be used on one side, whilenewsliner may be used on the opposite side.

Paper and cardboard facing materials may be made from recycled fibers(e.g., used corrugated paper, Kraft cuttings, or waste newsprint), butthey may also be partially or wholly made from virgin fibers. Othernatural or synthetic fibrous materials also can be used, including thosederived from metals or glass (e.g., fiberglass mat, chopped orcontinuous strand mat, or glass roving, both woven and non-woven). Otheruseful materials for the facing sheet include filament forming syntheticorganic polymers (e.g., nylon, polyesters, polypropylene, polyethylene,rayon, and cellulosics), ceramics, cotton, cloth, hair, felt, and thelike. Fibrous mats can be bound with, or coated with a resin binder.Multiple layers of fibrous materials, for example a composite sheet of aglass mat and Kraft paper, may also be used.

In certain embodiments, one or both of the mat facers may be coated, onthe external and/or internal surfaces of the mat facer, to provideadditional performance characteristics of the panel and/or facer.

It has been discovered that incorporation of a halide salt sequestrationagent into the gypsum slurry is effective to remove salts, such aschloride salts, from the resulting set gypsum composition, to reduce theimpact of those salts on the resulting gypsum panel properties. Inparticular, it has been found that these agents can be added to a gypsumcomposition with high chloride salt content and the facer to core bondstrength returns to expected performance levels absent the chloridesalts. For example, these compositions may be of particular use inpanels having paper facers, because the halide salt sequestration agentmay reduce the impact of salts on the paper to core bond strength. Forexample, gypsum panels of the present disclosure may display a paperfacer to core humid bond strength of at least about 12 lbs/force.

As compared to alternative methods of washing the salt content from thegypsum material and disposing of the high salt content water, thisdisclosure allows for the sequestration of salts inside the halide saltsequestration agent, trapping the salt inside the wallboard. As such, itis believed that the present disclosure reduces the environmental impactof the gypsum cleaning process.

Gypsum Panels & Systems

Gypsum panels, and systems of such panels, are also provided herein. Thegypsum panels may be manufactured to have any of the properties, or viaany of the methods, described herein. In certain embodiments, a gypsumpanel contains a gypsum core that comprises set gypsum and a halide saltsequestration agent, wherein the halide sequestration agent sequestersat least a portion of halide salt present in the gypsum core. Forexample, such panels may display enhanced strength and facer bondingproperties.

In certain embodiments, as shown in FIG. 1, a gypsum panel 100 includesa gypsum core 101 having a first surface and a second opposed surface,and a first facer mat 104 associated with the first surface of thegypsum core 101, such that gypsum of the gypsum core penetrates and/oradheres to at least a portion of the first facer mat 104. The variouslayers are illustrated as separate layers in the figures for ease ofillustration; however, it should be understood that overlap of thesematerials may occur at their interfaces.

In certain embodiments, as shown in FIG. 2, the gypsum core 101 includestwo or more gypsum layers 102, 108. For example, the gypsum core mayinclude various gypsum layers having different compositions. In someembodiments, the first gypsum layer 102 that is in contact with thefacer mat 104 is a slate coat layer, as discussed above. In someembodiments, the first gypsum layer 102 is present in an amount fromabout 5 percent to about 20 percent, by weight, of the gypsum core 101.In certain embodiments, as shown in FIG. 2, the gypsum panel 100includes two facer material mats 104, 112 that are associated with thegypsum core 101.

As discussed above, the panels may have a thickness from about ¼ inch toabout 1 inch. For example, the panels may have a thickness of from about½ inch to about ⅝ inch.

Building sheathing systems are also provided herein, and include atleast two of gypsum panels described herein, including any features, orcombinations of features, of the panels described herein. For example,the gypsum panels may each include a gypsum core containing a halidesalt sequestration agent. In certain embodiments, as shown in FIG. 4, abuilding sheathing system includes at least two gypsum panels 300 and aseaming component 320 configured to provide a seam at an interfacebetween at least two of the gypsum panels 300. In certain embodiments,the seaming component comprises tape or a bonding material.

EXAMPLES

Gypsum panels formed from gypsum slurries containing halide saltsequestration agents, as disclosed herein, were manufactured and testedaccording to the following examples.

Example 1

Sample gypsum boards were manufacturing according to the followprocess. 1. Gather four 4 in×4 in×0.5 in molds, arranging them in tworows of two, and place paper in them with the bond side facing up. 2.Weigh and hand mix all dry materials (e.g., stucco, starch, CaCl₂),experimental additive, etc.), typically 450 g of dry material is enough.3. In a separate container, weigh and mix wet material until homogenous,(e.g., water, dispersant). 4. In a separate container, gather foam (1%soap solution) from foam generator and transfer desired amount of foaminto its own container. 5. Initiate mix by dumping all contents of thedry mix into the wet mix solution, then mixing them with a high shearmixer at 1352 RPM for 5 seconds, or until slurry is consistent and freeof lumps. 6. Dump slurry into foam container and mix with high shearmixer for 5 seconds, gently swirling and shaking the container so thatthe foam is mixed into slurry. 7. Pour slurry into the molds. 8. In atimely manner, use a 6 in or greater scraping knife to wipe off excessslurry from the top of the molds by gently scraping across the molds inone motion. 9. Adhere bond side of paper to the exposed surface of theslurry. 10. Place a 12 in×12 in glass on top of the molds. Prior tomixing, make sure glass is even and clean of debris. 11. Allow 5 to 10minutes for slurry to set. 12. Remove boards and record weight. Weightof samples should be consistent with each other. 13. Wrap in aluminumfoil and place in convection oven at 104° C. for 30 minutes. 14.Transfer to convection dryer at 110° F. for about 16 hours. 15. Recordweight.

To evaluate the effect of an activated alumina halide salt sequestrationagent to mitigate the decrease in humid bond strength typically observeddue to the presence of salt, sample boards were made according to thefollowing compositions in Table 1.

TABLE 1 Example 1 Experimental Gypsum Board Formulations Neat 1 lb/msf 5lb/msf 10 lbs/msf 15 lbs/msf 20 lbs/msf 1 lb/msf 5 lb/msf 10 lbs/msf 15lbs/msf 20 lbs/msf Board AA AA AA AA AA AA AA AA AA AA Control T1 T2 T3T4 T5 T1C T2C T3C T4C T5C Stucco, g 442.88 442.50 440.99 439.12 437.26435.42 442.50 440.99 439.12 437.26 435.42 Starch, g 3.85 3.85 3.83 3.823.80 3.79 3.85 3.83 3.82 3.80 3.79 CaCl₂ 1.8 1.8 1.8 1.8 1.8 1.8 0 0 0 00 (96%, Anhydrous) Activated 0 0.38 1.92 3.82 5.70 7.57 0.38 1.92 3.825.70 7.57 Aluminum (28 × 48 Mesh, (0.7 mm particle size)) Dispersant, g3.27 3.27 3.26 3.25 3.23 3.22 3.27 3.26 3.25 3.23 3.22 Foam, g 20-2320-23 20-23 20-23 20-23 20-23 20-23 20-23 20-23 20-23 20-23 Water, g460.59 460.20 458.63 456.68 454.75 452.84 460.20 458.63 456.68 454.75452.84

After the samples were manufactured, they were subjected to a humid bondforce test, according to the following test procedure. 1. Once sampleshave been dried for ˜12 hours at 100° F., allow samples to preconditionby sitting in ambient atmosphere for 30 minutes. 2. Set conditioningcabinet to 90% relative humidity and 90° F. 3. Prior to placing inconditioning cabinet, score samples 1.25 in from the edge, across thesample using humid bond jig. 4. Once conditions have been achieved, in10 minute intervals, place a set of 6 samples in conditioning cabinet.5. Once an hour has elapsed from the first set, take out first set ofsamples. 6. Snap the board along the score, making sure not to peel anypaper. 7. Place in Humid Bond testing apparatus on United Tester. 8.Test and record humid bond in lbs/F. 9. Check and record percentage bondfailure.

The samples were tested accordingly and the results are shown in Table 2below and are graphically depicted in FIG. 5.

TABLE 2 Example 1 Humid Bond Test Results Control T1 T2 T3 T4 T3C T4CNeat 1#/msf 5#/msf 10#/msf 15#/msf T1C T2C Neat Neat Stucco, C2 Alum +Alum + Alum + Alum + Neat Neat 10#/ 15#/ Disp., 1800 ppm 1800 ppm 1800ppm 1800 ppm 1800 ppm 1#/msf 5#/msf msf msf Starch CaCl₂ CaCl₂ CaCl₂CaCl₂ CaCl₂ Alum Alum Alum Alum 14.3 10.8 12.5 13.0 10.8 13.4 13.2 11.913.0 12.6 15.6 8.6 10.6 13.7 10.6 14.9 14.6 13.3 13.6 13.0 16 10.9 11.912.8 10.2 12.7 14.5 12.5 14.6 14.6 15.6 11.1 12.6 10.7 12.9 11.2 9.014.4 16.6 14.3 13.2 10.1 10.4 9.5 13.0 11.3 11.8 13.4 15.8 13.7 13.2 8.78.2 7.7 13.3 13.7 13.8 12.1 16.8 16.1 14.4 7.8 9.1 13.1 14.9 12.3 16.212.4 11.6 12.5 13.2 8.2 9.1 16.2 13.0 13.9 15.2 12.0 11.4 12.0 15.6 10.310.3 10.4 11.8 16.9 14.7 15.5 13.9 12.7 11.9 10.4 8.6 11.1 14.7 16.412.8 13.7 14.9 14.5 11.4 10.3 10.5 11.9 14.6 12.9 12.5 12.3 16.7 12.514.6 9 10.7 11.0 11.5 14.0 14.7 14.0 16.0 14.0 Average 14.1 9.7 10.411.8 12.6 13.6 13.6 13.1 14.6 13.5 lbs/force Standard 1.5 1.1 1.4 2.21.6 1.8 1.9 1.1 1.9 1.2 Dev S. 0.438 0.332 0.418 0.637 0.472 0.513 0.5500.324 0.551 0.346 Error

As is illustrated by these results, for the samples containing calciumchloride, the greater amount of loading of activated alumina results inincreased humid bond strength, with 15 lb/msf loading of activatedalumina showing comparable or better humid bond strength to an otherwiseidentical sample without the salt.

Thus, the gypsum panels made by the methods disclosed herein may displayan average lbs/force, as measured in the above-described humid bondtest, of from 80 percent up to 100 percent, or greater, of the strengthdisplayed by an otherwise identical board having no, or negligible,gypsum salt content.

Example 2

Next, the bench model boards described in Example 1 were compared tosample boards made to standard board size (i.e., full size) andproperties, to determine whether the impact of the halide saltsequestration agent scaled to full size boards. The humid bond testdescribed above was conducted on these boards and a nail pull test wasconducted according to the following process. 1. Once samples have beendried for ˜12 hours at 100° F., allow to precondition at ambientatmosphere until constant weight is achieved. 2. Record weight. 3. Usinga drill press, drill a 7/64″ diameter hole through the center of eachsample. 4. Place sample onto testing stage of United Tester, in whichthe 3″ diameter hole in the middle of the stage is in the middle of thetesting sample. 5. Lower nail shank close to the 7/64″ hole of thesample, but not touching. 6. Zero the load indicator and begin test. 7.Record nail pull resistance as lbs/force.

The comparative results of the humid bond test and the nail pull test,for the benchtop and standard size boards, are illustrated in the graphsof FIGS. 6 and 7, respectively. As can be seen, the full size boardsdisplayed the same trend as was observed with the bench top boardsamples. Namely, as the salt content of the full size boards decreased(i.e., through increased addition of salt sequestration agents), thehumid bond performance and nail pull performance increased.

Example 3

Next, the effect of the activated alumina on the chloride concentrationin natural gypsum and FGD samples was investigated using ionchromatography.

First, the gypsum/FGD materials were calcined according to the followingprocedure. 1. Check initial total water percent of gypsum/stucco. Ifsample is 22-27%, allow to dry in convection oven t at 100° F. overnightto achieve 17-19% total water. 2. S et convection oven to 330° F. (165°C.) and allow to achieve set point. 3. Spread out gypsum in an even,thin layer, approximately 2-3 inches deep, in a wide pan or casseroledish. 4. Place pan in the oven. 5. In 10 minute intervals, remove panand stir gypsum, to ensure even drying, and return to oven. 6. Measureand record total water analysis. 7. Calcining has been achieved oncetotal water of 4-6% has been achieved.

Next, sample boards were made according to the following procedure. 1.Gather two 4 in×4 in×0.5 in molds. 2. Once gypsum has been calcined tostucco, weigh up dry material (stucco and/or experimental additives). 3.In separate container, weigh out water. 4. Pour dry material intoaqueous solution, and mix using high shear mixer for 5 seconds untilconsistent. 5. Pour slurry into molds. 6. Wrap in foil and dry inconvection oven at 104° C. for 30 minutes. 7. Transfer to convectiondryer set at 100° F. overnight. 8. Grind samples to powder using rockcrusher and pulverizer.

Next, the salt (sodium and chloride) content of the samples is testedaccording to the following procedure. 1. Place 10 grams of preparedsample in a 250 ml beaker (Samples are tested in duplicates). 2. Add 100ml of deionized water to each beaker. 3. Cook (use hot plate) samplesfor 20 minutes at low temperature. 4. Stir occasionally. 5. Aftersamples have been heated as directed, vacuum filtrate the entiresolution of each beaker through a large funnel into 500 ml Erlenmeyerflask. 6. Wash stirring rod and beaker with deionized water. 7. Allowfiltrate to cool. 8. Measure 50 ml of solution using a 50 ml graduatedcylinder. 9. Pour the solution into a 100 ml volumetric flask. 10. Rinsecylinder thoroughly with deionized water and pour into volumetric flask.11. Fill volumetric flask to the mark with deionized water. 12. Mixsolution thoroughly. 13. Once solutions are made and standards are ran,place samples in ion chromatography instrument. 14. Run chlorides andthen sodiums to give total salt results.

The results of these tests for various sample formulations are shown inTable 3 below and are represented graphically in FIG. 8.

TABLE 3 Example 3 Experimental Results Low High Low CaCl₂ High CaCl₂Neat CaCl₂ ppm + CaCl₂ ppm + Neat FGD + FGD + Sample Stucco (600 ppm)15#AA (1800 ppm) 15#AA FGD 5#AA 15#AA NaCl % 0.008 0.011 0.017 0.0100.018 0.020 0.017 0.024 Na₂SO₄ % None None None None None None None NoneCaCl₂ % 0.025 0.138 0.097 0.187 0.157 0.105 0.103 0.082 Total Salt,10.531 47.742 36.378 63.256 55.957 40.075 38.411 34.011 Oz/Ton TotalSalt, 329.09 1491.95 1136.81 1976.74 1748.66 1252.36 1200.33 1062.84 ppmNa⁺ conc., 1.57 2.08 3.39 1.98 3.40 3.89 3.20 4.84 ppm 1.54 2.41 3.182.05 3.78 4.17 3.47 4.59 Cl⁻ conc., 10.48 45.79 37.51 65.13 57.18 38.4335.92 34.16 ppm 10.29 49.16 34.58 60.83 53.95 40.92 40.22 32.97 Average10.39 47.48 36.05 62.98 55.57 39.68 38.07 33.57 Cl Difference 11.437.415 1.605 6.11 Cl Total salt 355.14 228.08 52.03 189.51 Diff

As can be seen in FIG. 8, the FGD displayed a high salt content ascompared to the naturally occurring gypsum. The naturally occurringstucco was doused with calcium chloride to mimic the impact of anaturally occurring high or low salt content in the lab. The increasedpresence of activated alumina resulted in a corresponding reduction inthe concentration of chloride ions detectable.

Next, the impact of various amounts of activated alumina on stuccodoused with low (600 ppm) and high (1800 ppm) concentrations of calciumchloride and on FGD having a relatively high salt content, on overallsalt content, was tested using ion chromatography. The results are shownin Table 4 below and graphically in FIG. 9.

TABLE 4 Further Example 3 Experimental Results Low Salt 600 ppm Conc. +CaCl₂ + 1800 ppm FGD + FGD + Stucco 600 ppm 15#AA 15#AA 1800 ppm CaCl₂ +FGD FGD + 15#AA 15#AA Sample Control CaCl₂ 3/16″ 0.7 mm CaCl₂ 15#AAControl 5#AA 3/16″ 0.7 mm NaCl, % 0.0079 0.0114 0.010 0.0167 0.01020.0183 0.0205 0.0170 0.021 0.0240 Na2SO4, % None None None None NoneNone None None None None CaCl2, % 0.0250 0.1378 0.122 0.0970 0.18740.1566 0.1047 0.1031 0.095 0.0823 Total 10.5309 47.7424 42.227 36.377963.2556 55.9571 40.0754 38.4105 36.962 34.0110 Salt, Oz/ton Total 329.11492.0 1319.6 1136.8 1976.7 1748.7 1252.4 1200.3 1155.1 1062.8 Salt, ppmDifference 329.1 172.4 355.1 228.1 52.0 97.3 189.5

As can be seen, at both the low and high salt concentrations in thenatural stucco, the activated alumina is effective at reducing theamount of salt found in the ion chromatography. Likewise, in the FGDsamples, the greater amounts of activated alumina reduced the amount ofsalt identified in the sample.

Example 4

Next, the impact of the particle size (4.7 mm versus 0.7 mm) of theactivated alumina salt sequestration agent was tested via IC analysis,as described in prior Examples. The experimental results are shown belowin Tables 5-7, and graphically in FIG. 10.

TABLE 5 Example 5 Experimental Results 600 ppm 1800 ppm Stucco 600 ppmCaCl₂ + 1800 ppm CaCl₂ + FGD FGD + FGD + Sample Control CaCl₂ 15#AACaCl₂ 15#AA Control 5#AA 15#AA NaCl % 0.008 0.011 0.017 0.010 0.0180.020 0.017 0.024 Na₂SO₄ % None None None None None None None None CaCl₂% 0.025 0.138 0.097 0.187 0.157 0.105 0.103 0.082 Total 10.531 47.74236.378 63.256 55.957 40.075 38.411 34.011 Salt, Oz/Ton Total 329.091491.95 1136.81 1976.74 1748.66 1252.36 1200.33 1062.84 Salt, ppm Na⁺1.57 2.08 3.39 1.98 3.40 3.89 3.20 4.84 conc., 1.54 2.41 3.18 2.05 3.784.17 3.47 4.59 ppm Cl⁻ 10.48 45.79 37.51 65.13 57.18 38.43 35.92 34.16conc., 10.29 49.16 34.58 60.83 53.95 40.92 40.22 32.97 ppm

TABLE 6 Further Example 5 Experimental Results 600 ppm + 1800 ppm +FGD + FGD + 1800 ppm + Sample 15#AA 3/16 15#AA 3/16 5#AA 3/16 15#AA 3/1615#AC NaCl % 0.010 0.013 0.017 0.021 0.011 Na₂SO₄ % None None None NoneNone CaCl₂% 0.122 0.248 0.122 0.095 0.246 Total Salt, 42.227 83.48944.442 36.962 82.212 Oz/Ton Total Salt, 1319.60 2609.02 1388.81 1155.062569.13 ppm Na⁺ conc., 1.88 2.35 3.29 3.94 2.26 ppm 1.86 2.72 3.52 4.172.22 Cl⁻ conc., ppm 29.68 84.70 45.68 36.55 83.10 44.32 81.57 42.4936.58 80.67 Average 37.00 83.135 44.085 36.565 81.885

TABLE 7 Further Example 5 Experimental Results Low Low ppm ppm CaCl₂ +CaCl₂ + FGD + FGD + 15 lbs/ 15 lbs/ 15 lbs/ 15 lbs/ High Low msf msf msfmsf High CaCl₂ Neat ppm 4.7 mm 0.7 mm Neat 4.7 mm 0.7 mm CaCl₂ ppm +FGD + Sample Stucco CaCl₂ AA AA FGD AA AA ppm 15#AA 5#AA Average 10.3947.48 37 36.05 39.68 36.60 33.57 62.98 55.57 38.07 Cl Total 329.1 1491.91319.60 1136.8 1252.4 1155.06 1062.8 Salt % Cl− −22.06% −24.08% −7.75%−15.40% % total −11.55% −23.80% −7.77% −15.14% Salt

As can be seen, while all samples containing activated alumina wereeffective at reducing the impact of the salt content of the samples, thesmaller particle size activated alumina was even more effective, whichis believed to be due to its increased surface area per mass.

Example 5

Additionally, the effect of a halide salt sequestration agent containingperlite, in expanded and unexpanded (raw) form, on salt concentrationwas tested via ion chromatography. The experimental formulations asshown below in Table 8.

TABLE 8 Example 5 Formulations Experimental 1 Experimental (CC 2 (CCExperimental Stucco + Stucco + 3 (FGD + Experimental 4 Salt + Raw Salt +Raw (FGD + Experimental unexpanded expanded FGD Unexpanded ExpandedControl Control Perlite) Perlite) Control Perlite) Perlite) Stucco, g200 200 200 200 FGD, g 200 200 200 CaCl₂, g 0.65 0.65 0.65 Raw 2.61 2.61Perlite, unexpanded, g Perlite, 2.61 2.61 Expanded, g Water, g 160 160160 160 160 160 160

As in prior Examples, the stucco was doused with CaCl₂ to achieve highsalt concentration, 1800 ppm, made into a board then grinded up for IC.FGD was dried to 4-6% total water, made into a board then grinded up forIC.

The ion chromatography results for these samples are shown below inTable 9 and graphically in FIG. 11.

TABLE 9 Ion Chromatography Results for Example 5 CC CC Stucco + Stucco +Salt + Salt + FGD + 15 lbs 15 lbs 15 lbs FGD + Experimental Unexp.expanded FGD Unexp. 15 Exp Sample Control Control Perlite Perl ControlPerlite Perl NaCl % 0.002 0.002 0.002 0.003 0.015 0.014 0.015 Na₂SO₄ %None None None None None None None CaCl₂ % 0.017 0.245 0.231 0.234 0.1390.145 0.111 Total Salt, 6.141 79.045 74.721 75.773 49.233 50.744 40.334Oz/Ton Total Salt, 191.91 2470.16 2335.02 2367.9 1538.52 1585.75 1260.42ppm Difference 0.014 −0.011 0.006 0.028 Cl Difference 135.14 102.2647.23 278.1 Total Salt %, Total 5.47% 4.14% 3.07% 18.08% Salt

As can be seen, both the unexpanded and expanded forms of perlite wereeffective to reduce the impact of salt in the samples.

Example 6

Further samples utilizing perlite as the halide salt sequestration agentwere manufactured according to the formulations outlined in Table 10.

TABLE 10 Experimental Formulations for Example 6 Control - ExperimentalExperimental C0 Control - C1 Control - C2 Control - C3 Raw LightweightHigh Salt High Salt + 5 lbs High Salt + Materials Formulationconcentration AA 15 lbs AA Stucco, g 442.88 442.88 440.99 437.26 Water,g 398.59 398.59 396.89 393.54 (w/s ratio) Starch, g 3.85 3.85 3.83 3.80Dispersant, g 3.27 3.27 3.26 3.23 CaCl2, g — 1.80 1.80 1.80 Perlite, — —— — Unexpanded g Perlite, — — — — expanded g Activated — — 1.92 5.70Alumina, g Soap, #/msf 1% solution 1% solution 1% solution 1% solutionPaper 54 lbs face 54 lbs face 54 lbs face 44 lbs 54 lbs face 44 lbs back44 lbs back back 44 lbs back T1 T2C T3C T3 T4C T4 T1C High 15 lbs/ T2 5lbs/ High 15 lbs/ High 5 lbs/msf Salt + msf High msf Salt + msf Salt +Neat 5 lbs Neat Salt + 15 lbs Neat 5 lbs Neat 15 lbs Raw UnexpandedUnexpanded Unexpanded Unexpanded Expanded Expanded Expanded ExpandedMaterials Perlite Perlite Perlite Perlite Perlite Perlite PerlitePerlite Stucco, g 440.99 440.99 437.26 437.26 440.99 440.99 437.26437.26 Water, g 396.89 396.89 393.54 393.54 396.89 396.89 393.54 393.54(w/s ratio) Starch, g 3.83 3.83 3.80 3.80 3.83 3.83 3.80 3.80Dispersant, g 3.26 3.26 3.23 3.23 3.26 3.26 3.23 3.23 CaCl2, g — 1.80 —1.80 — 1.80 — 1.80 Perlite, 1.92 1.92 5.7 5.70 — — — — Unexpanded gPerlite, — — — — 1.92 1.92 5.7 5.70 expanded g Activated — — — — — — — —Alumina, g Soap, 1% 1% 1% 1% 1% 1% 1% 1% #/msf solution solutionsolution solution solution solution solution solution Paper 54 lbs 54lbs 54 lbs 54 lbs 54 lbs 54 lbs 54 lbs 54 lbs face 44 lbs face 44 lbsface 44 lbs face 44 lbs face 44 lbs face 44 lbs face 44 lbs face 44 lbsback back back back back back back back

Humid bond tests were conducted on these samples, with the results shownbelow in Tables 11 and 12 and in FIGS. 12 and 13.

TABLE 11 Humid Bond Test Results for Perlite Compositions StError WithSample Salt No Salt Salt StError w/o salt Neat 15.5 0.283660875 HighSalt 13 0.3494849 5# Popped 14.4 14.6 0.3134112 0.352239857 Perlite withSalt 15# Popped 10.8 15 0.3257643 0.502034922 Perlite with Salt 5# RawPerlite 13.3 0.4427071 with Salt

TABLE 12 Humid Bond Test Results for Perlite Compositions Humid Bond St.Error Neat Stucco 15.5 0.2836 High Salt 13 0.3494 Stucco High Salt 14.40.3134 Stucco + 5# Popped Perlite High Salt 10.8 0.3257 Stucco + 15#Popped Perlite Neat Stucco + 14.6 0.3522 5# Popped Perlite Neat Stucco +15 0.502 15# Popped Perlite

As can be seen, the expanded perlite was effective at mitigating theimpact of the salt, allowing for improved bond strength between thegypsum core and the paper facer, as compared to gypsum panels in whichno salt sequestration agent is present.

Thus, it has been discovered that the negative impact of salt present invarious forms of gypsum may be mitigated utilizing certain saltsequestration agents. Panel strength and core-paper facer bond strengthmay be improved by utilizing halide salt sequestration agents in amountseffective to sequester at least a portion of any salt present in thegypsum stucco.

While the disclosure has been described with reference to a number ofembodiments, it will be understood by those skilled in the art that theinvention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions, or equivalent arrangements not describedherein, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A method of making a gypsum panel, comprising: combining gypsumstucco and a halide salt sequestration agent with water to form a gypsumslurry; and setting the gypsum slurry to form at least a portion of agypsum core, wherein the halide salt sequestration agent is present inan amount effective to sequester at least 25 percent, by weight, ofhalide salt present in the gypsum stucco.
 2. The method of claim 1,wherein the halide salt sequestration agent comprises alumina orperlite.
 3. The method of claim 1, wherein the halide salt sequestrationagent comprises activated alumina present in an amount of from about0.01 to about 10 weight percent, by weight of the gypsum stucco.
 4. Themethod of claim 3, wherein the activated alumina has an average particlesize of less than 1 mm.
 5. The method of claim 1, wherein the halidesequestration agent comprises perlite present in an amount in an amountof from about 0.01 to about 10 weight percent, by weight of the gypsumstucco.
 6. The method of claim 5, wherein the perlite is perlite orehaving an average particle size smaller than 30 mesh.
 7. The method ofclaim 5, wherein the perlite is expanded perlite having an averageparticle size smaller than 16 mesh.
 8. The method of claim 1, furthercomprising heating the halide sequestration agent prior to combining thehalide sequestration agent with the gypsum stucco, wherein the heatingis effective to expand or activate at least a portion of the halidesequestration agent.
 9. The method of claim 1, further comprisingassociating a facer material with the gypsum slurry or the gypsum core.10. The method of claim 9, wherein: the facer material comprises a paperfacer material, and the gypsum panel displays a paper facer to corehumid bond strength of at least about 12 lbs/f.
 11. The method of claim1, wherein the gypsum stucco comprises gypsum obtained from a naturalsource or from a flue gas desulfurization process.
 12. A gypsum panel,comprising: a gypsum core that comprises set gypsum and a halide saltsequestration agent; wherein the halide sequestration agent is presentin an amount effective to sequester at least 25 percent, by weight, ofhalide salt present in the gypsum core.
 13. The gypsum panel of claim12, wherein the halide salt sequestration agent comprises alumina orperlite.
 14. The gypsum panel of claim 12, wherein the halide saltsequestration agent comprises activated alumina present in an amount offrom about 0.01 to about 10 weight percent, by weight of the set gypsum.15. The gypsum panel of claim 14, wherein the activated alumina has anaverage particle size of less than 1 mm.
 16. The gypsum panel of claim12, wherein the halide sequestration agent comprises perlite present inan amount in an amount of from about 0.01 to about 10 weight percent, byweight of the gypsum stucco.
 17. The gypsum panel of claim 16, whereinthe perlite is perlite ore having an average particle size smaller than30 mesh.
 18. The gypsum panel of claim 16, wherein the perlite isexpanded perlite having an average particle size smaller than 16 mesh.19. The gypsum panel of claim 12, further comprising a facer materialassociated with the gypsum core.
 20. The gypsum panel of claim 19,wherein: the facer material comprises a paper facer material, and thegypsum panel displays a paper facer to core humid bond strength of atleast about 12 lbs/f.